avoiding collision by eye or radar 137
shadow. Freeboard, or the height of a vessel from its deck to the waterline, can
exceed 100 feet on large ships. If the offi cer on watch is in a pilothouse near the
stern, he’s looking diagonally over the bow and may lose vessels in this freeboard
shadow. Or the offi cer could be daydreaming—relying on the radar to sound
an alarm if a target comes within range. In addition, radar signals travel in a
straight line and can skip over a small craft below the line-of-sight plane.
Always assume a large ship does not see you. In this case, you must abandon
the stand-on or give-way vessel rules and take action right away.
Change course 90 degrees. Immediately turn to bring the other vessel’s
bow abeam. If you see more of the vessel’s starboard side, turn 90 degrees to
keep its starboard side visible. If you see more of its port side, turn 90 degrees
to keep its port side visible.
Increase to maximum speed. Power vessels should increase speed to the
highest RPMs available. Sailing vessels under sail should start the engine and
increase to maximum RPMs; if the engine fails to start or you have no engine,
trim your sails for best speed.
Signal and illuminate. Sound the danger signal (continuous short blasts
on the whistle or foghorn). In nighttime, turn on your cabin and deck light-
ing. Illuminate the flying bridge, hull, or sails.
All hands into life jackets. All hands on board should get life jackets
on now! If you are wearing an inflatable, pull the CO 2 cartridge or use the
manual tube to inflate the bladders.
Take constant drift bearings. Take constant drift bearings to the vessel’s bow
and stern. Th e bearing should change rapidly as each vessel moves away from the
other.
SEA-CRET TIP
X It’s tempting to jump on the radio, but this diverts your attention from
the situation at hand. Establishing communications takes time. A 20-
knot tanker half a mile away will run you over in less than 90 seconds.
(60 ÷ 20 = 3 minutes to travel 1 mile, or 90 seconds to travel^1 / 2 mile).
Better move now!How to Identify Motionless Contacts on Your Radar
Two types of contacts present hazards in our path: those with motion and
those without. You’ve probably laid your track from buoy to buoy or light to
light. So let’s look at how to identify fi xed or fl oating structures.